1. Field of the Invention
The present invention relates generally to a recording head of an ink-jet type for emitting droplets of an ink contained in an ink chamber for forming dots on a recording sheet by the kinetic energy of an electromechanical conversion means such as a piezo-electric vibrator or the like. More specifically, the invention relates to a configuration of nozzles of the recording head.
2. Related Art
A conventional recording head of the ink-jet type for emitting ink droplets to form characters or figures on a recording sheet as a set of dots is generally provided with a pressure chamber and a thin nozzle plate disposed to surround the pressure chamber, on which plate nozzles in a required number are formed.
The apparatus employing the thin nozzle plate has an advantage that the nozzles can easily be formed and also that the axial length of a nozzle relative to an diameter of its orifice can be limited within a predetermined range so that the efficiency of the ink emission can be improved.
However, in case that the diameter of the orifices is made smaller to emit small ink droplets thereby to improve the printing quality, it is necessary to employ a thinner nozzle plate accordingly. In this case, the rigidity of the thin plate is an important concern. Particularly, in case of the apparatus employing a piezoelectric vibrator as an ink droplet emitting member, if the nozzle plate is made extremely thin, it is readily deformed thereby emitting ink droplets in incorrect directions, especially in case of applying a load of 1-5 kg/cm.sup.2 with high frequency repeatedly to the nozzle plate.
An apparatus has been proposed to resolve the aforementioned problem, as disclosed in U.S. Pat No. 4,282,533, which is provided with a nozzle plate having a sufficient thickness and grooves formed on the back thereof. According to this apparatus, the required number of nozzles are arranged on the bottom of the grooves. However, this type of thin nozzle plate still suffers from problems of another aspect. That is, even when one of the selected piezoelectric vibrators is actuated, the pressure causes a stress concentration along the longitudinal direction of the grooves so that the nozzle plate will largely bend, or the applied pressure propagates along the groove thereby to cause an undesired crosstalk phenomenon.